Pregnancy rates of introduced red deer in Patagonia, Argentina after a period of drought

FLUCK, WT; SMITH-FLUECK, JM

Nashville, Tenn., USA

Conferencia; The Wildlife Society Annual Conference; 2000

Red deer (Cervus elaphus) were introduced to Patagonia in the 1920´s and have reached high densities in certain areas of the forest-steppe ecotone. Severe drought conditions during summer/fall of 1999 were suspected to have an impact on reproduction of red deer. Necropsies of 50 adult females revealed a pregnancy rate of only 56% as compared to 100% in 1996. The age distribution of pregnant females reflects the importance of not having been pregnant during the previous cycle. The primiparous three-year-old females had a 77% pregnancy rate whereas none of  the lactating females were pregnant. Normally a higher reproductive success occurs for middle age classes, thereby reducing the chances of becoming pregnant during stress periods which was reflected in this study in the age distribution of non-pregnant females. Chest girth as an index of body size and median age, however, was not different for pregnant and non-pregnant females. Body fat reserves were severely depleted in most animals irrespective of reproductive status. The results indicate that these red deer populations occur at densities where they can easily become food-limited through a singular environmental phenomenon such as a drought period. Although the recruitment rate will be drastically reduced through such food shortage, red deer will continue to exert intensive pressure on the flora causing subsequent damage if population densities are not lowered through hunting.